1. Field of the Invention
The present invention relates to a substrate treatment apparatus and a substrate treatment method for treating a substrate with a treatment liquid. Examples of the substrate to be treated include semiconductor wafers, glass substrates for liquid crystal display devices, substrates for plasma display devices, substrates for FED (Field Emission Display) devices, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, substrates for photo masks, ceramic substrates, and substrates for solar cells.
2. Description of Related Art
In production processes for semiconductor devices and liquid crystal display devices, substrates such as semiconductor wafers and glass substrates for liquid crystal display panels are treated with a treatment liquid. A substrate treatment apparatus of a single substrate treatment type adapted to treat a single substrate at a time includes a spin chuck which horizontally holds and rotates the substrate, and a nozzle which supplies the treatment liquid to a front surface (to-be-treated surface) of the substrate. The substrate is held by the spin chuck with its front surface up. Then, the treatment liquid is supplied from the nozzle to a center portion of the front surface of the substrate, while the substrate is rotated by the spin chuck. The treatment liquid supplied to the front surface of the substrate receives a centrifugal force generated by the rotation of the substrate to spread from the center portion toward a peripheral edge of the substrate on the front surface of the substrate (see US2009/0032067A1).
When the treatment liquid is spouted from the nozzle with the substrate being rotated by the spin chuck, the treatment liquid spouted from the nozzle is supplied to the center portion of the front surface of the substrate. Thus, a generally round liquid film of the treatment liquid is formed on the front surface of the substrate. The liquid film receives the centrifugal force generated by the rotation of the substrate to spread toward the peripheral edge of the front surface of the substrate.
However, the liquid film of the treatment liquid does not spread generally roundly toward the peripheral edge of the substrate, but often spreads radially before reaching the peripheral edge of the front surface of the substrate. The spreading state of the liquid film of the treatment liquid is shown in FIG. 9. The generally round liquid film of the treatment liquid spreading on the front surface of the substrate includes a plurality of linear liquid film portions L extending radially outward from an outer periphery of the liquid film. This is because the outer periphery of the liquid film of the treatment liquid spreads outward along more hydrophilic portions of the front surface of the substrate.
It may be possible to reliably cover the entire front surface of the substrate with the treatment liquid, for example, by spouting the treatment liquid from the nozzle at a higher flow rate (e.g., at 2.0 L/min or higher). However, this increases the amount of the treatment liquid required for treating a single substrate, and correspondingly increases treatment costs.